Non-steroidal anti-inflammatory analgesic agents do not exhibit such serious side effects as exhibited in steroidal anti-inflammatory analgesic agents, and are widely used in a clinical field.
However, these non-steroidal anti-inflammatory analgesic agents have a disadvantage to still cause various side effects such as gastro-intenstinal lesion although not to the extent that is caused by steroidal anti-inflammatory analgesic agents. In order to minimize such side effects, various dosage forms are now under extentisve investigation.
Recently, in order to overcome the above problems on side effects and maintain the drug effects for a long period of time, an administration method to percutaneously absorb the effective component is being watched. Various ointments and adhesive preparations containing an effective component so as to practically employ the administration method have been developed.
However, the skin has a stratum corneum containing keratin as a major component and further contains a large amount of a fat-soluble component such as fat, wax and cholesterol. Therefore, the skin has a physiological defensive function, a so-called "barrier function", and as a result, it is difficult to easily make a percutaneous absorption of a drug.
In particular, many of non-steroidal anti-inflammatory analgesic agents, the utility of which is highly valued, have a salt form, and the skin exhibits a strong barrier function against drugs having a salt form.
On the other hand, skin adhesive preparations are composed of a pressure-sensitive adhesive material comprising a rubber or acrylic high molecular weight material as a base material. These materials generally do not dissolve drugs sufficiently, and it is quite difficult to uniformly dissolve the drug having the salt form and maintain the dissolved state. Even if the drug in the skin adhesive preparation is prepared in the dissolved state, crystallization of the drug contained occurs during the storage, sometimes inhibiting the percutaneous absorption of the drug.